Danuta Kozak, Elżbieta Pogroszewska, Mariusz Szmagara

The influence of type and orientation of explants on in vitro growth and development of Cosmos atrosanguineus (Hook.) Voss

Abstract:Cosmos atrosanguineus is a tuberous, tender perennial with velvety, dahlia-like, brownish-red flowers that have a chocolate aroma. It is sterile, so no viable seeds are produced. This species is particularly suitable for a border plant in any perennial garden. A study was undertaken to determine whether shoot apex and leaf removal as well as explant orientation had an influence on axillary shoot induction. Explants were prepared from shoots taken from aseptically grown shoot cluster and were cultured for 6 weeks on Murashige and Skoog medium containing BA (1 mg·dm-3). The study results showed that the removal of the apex from the non-defoliated shoot tip improved axillary branching. The removal of developed leaves from the shoot tip with the apex removed caused a reduction in axillary shoot production. The defoliated shoot tip inserted vertically in the medium in an inverted position regenerated the highest number of axillary shoots characterized by the highest fresh weight. The defoliated shoot tip after removal of the apex, placed vertically with the base down, produced axillary shoots characterized by the greatest elongation growth and the highest percentage of shoots that reached a length of more than 1 cm.